Environmental DNA (eDNA) is genetic material collected from environmental samples — soil, water, sediment, snow or air — rather than directly from an organism. As animals and plants interact with their surroundings, they leave behind DNA through shed skin, mucus, faeces, hair and other biological traces, which can be extracted and sequenced to reveal which species are present in an ecosystem.
The technique enables large-scale biodiversity surveys without capturing or disturbing wildlife. Researchers use methods such as DNA metabarcoding to amplify and sequence thousands of genetic fragments from a single water or soil sample, then match them against reference libraries to identify everything from bacteria to mammals. The approach has proven especially valuable for detecting rare, elusive or endangered species that leave few visible signs, and for monitoring aquatic environments where traditional observation is difficult. In recent years eDNA has been adapted for tracking invasive species, assessing coral-reef health and even monitoring human pathogens during the COVID-19 pandemic.
eDNA sampling featured in our Field Notes coverage of rare deep-sea species detection and biodiversity monitoring in low-visibility ocean habitats.
